This invention relates to computer systems, and especially to computer systems that are employed as servers.
The systems may for instance be employed as servers for example in local area networks (LANS) or in wide area networks (WANs), telecommunications systems or other operations such as database management or as internet servers. Such servers may be used in so-called “horizontally scaled” applications in which tens or hundreds of corresponding servers are employed as part of a distributed system.
A typical computer employed for such purposes will comprise two or more processors mounted on a motherboard, together with power supply units (PSUs), and other components such as hard disc drives (HDDs), fans, digital video disc (DVD) players, memory modules, ethernet ports etc. One or more of the processors, the host processor(s), provides the main functions of the server, and may communicate with various internal parts of the system via a console interface. In addition, the or each host processor will communicate with a number of peripheral components, including communication ports, optionally via peripheral component interconnect (PCI) bridges in order to provide server operation.
In addition to the host processor(s), the system may include another processor, called the service processor or the remote management controller (RMC), which provides management functions for the system assembly. Such functions may include environmental monitoring, temperature monitoring of the enclosure, fan speed control, data logging and the like. The service processor may communicate with the host processor or with one of them, and may also have one or more external communication ports so that a user or network administrator can communicate with the service processor, or can communicate with the host processor(s) via the service processor. For example, the service processor may have its own ethernet network port for direct communication to the network administrator.
Such ethernet network ports, whether communicating with the service processor or the host processor(s) will normally need a physical interface (PHY) in order to clean the signals and to provide power for driving the signals along the ethernet cabling, clock timing, line coding etc. The signals will then typically be sent to the ethernet cabling via a standard network port, for example an RJ45 port which will accept an eight line cable and is provided with a pair of light emitting diode (LED) indicators, one for indicating the existence of a link, and the other for indicating the existence of traffic on the line.
If there is any malfunction of the service processor whether due to hardware or software faults, the system is designed to continue to operate, at least as far as the provision of services provided by the host processor are concerned, although clearly system management services will no longer be available until the service processor is replaced in the event of a hardware failure. Thus, the functioning of the server should be largely unaffected by any failure of the service processor.
However, one problem may occur. Even though the service processor has stopped functioning, power will still be sent to all the ethernet interfaces including the service processor ethernet interface. While this will not matter as far as the ethernet interfaces handled by the host processors are concerned because those interfaces will still be controlled by their associated media access controllers (MACs) and host processors, no such control is exerted on the management interface controlled by the service processor. Thus, internal lines in the system extending between the service processor and the management PHY may be susceptible to interference from any active components in the system, and in particular from the host processor(s). This interference will then be amplified and line coded by the management PHY before being sent to the ethernet lines visual inspection of the RJ45 management port will give the appearance that the server is functioning correctly because the LEDs will be on indicating traffic on the line, even though this traffic is simply interference, and the server will appear to accept data from the service administrator because the RJ45 port is still operational.